(1) Field of the Invention
The present invention relates to a display device where a transparent cover is pasted to the surface of a display panel via a viscous film.
(2) Related Art Statement
Liquid crystal display devices having a liquid crystal display panel, for example, are known as display devices. In many cases, a transparent cover, such as of an acryl resin, is provided on the viewer side (front side) of these liquid crystal display panels. This transparent cover functions as a protective cover plate. However, this transparent cover is provided at a predetermined distance from the liquid crystal display panel, and therefore, an air layer intervenes between the transparent cover and the liquid crystal display panel. Thus, unnecessary reflection occurs in the interface with this air layer due to the difference in the index of refraction, which becomes a factor of lowering the contrast of the display.
In order to solve this problem, a technology for pasting a transparent cover to the surface of the liquid crystal display panel using an adhesive or a viscous film has been proposed. FIG. 3 is a cross sectional diagram showing the structure of a conventional liquid crystal display device.
In FIG. 3, a liquid crystal display panel PNL has a structure where a first substrate 1 and a second substrate 2 are pasted together with a sealing material 3 in between so that a liquid crystal layer 6 is sandwiched between the first substrate 1 and the second substrate 2. In addition, a lower polarizing plate 4 and an upper polarizing plate 5 are provided on the first substrate 1 on the side opposite to the liquid crystal layer 6 and on the second substrate 2 on the side opposite to the liquid crystal layer 2, respectively.
A transparent cover 7 is pasted to the surface of this liquid crystal display panel PNL on the viewer side with an adhesive or a viscous film 12 in between. In addition, when the used adhesive or viscous film 12 has an index of refraction that is close to that of the transparent cover 7, unnecessary reflection can be prevented in the interface due to the difference in the index of refraction because no air layer intervenes, and thus, the contrast of the display can be increased.
In addition to the conventional structure shown in FIG. 3, the following Patent Document 1 can be cited as an example of the prior art relating to the present invention.    [Patent Document 1] Japanese Unexamined Patent Publication 2007-178758